From time to time, it is necessary to test circuit breakers to verify that they will actually trip at proper current values and with proper time delay. Manifestly, it is desirable that a circuit breaker trip at appropriate current values and with proper time delay to prevent or minimize damage to a device protected by the breaker and upon occurrence of an overcurrent condition.
Circuit breakers having solid state trip units usually depend upon a low power current source by which one of a number of preset values of current are injected into the trip circuit to simulate, for testing, an overcurrent condition. Testing of solid state trip circuits of a circuit breaker in this manner is advantageous in that it is not necessary to connect or disconnect energized conductors to the circuit breaker.
Associated with the testing procedure is a requirement of testing in the field where the circuit breakers are located. Heretofore, one type of test device has been a portable test unit that is powered by an external 120 AC power source which currently exists on the market. A disadvantage of such a test unit is that it is costly, bulky, and requires modification for the DC electronic trip unit. Accordingly, a need exists for a test device which is dependent only upon an internal power supply of the electronic trip unit being tested, whereby no additional power source is required to be connected to the test device.